Method of making tubing



July 27, 1965 H. A. FROMSON 3,196,657

METHOD OF MAKING TUBING Filed July 16, 1959 2 Sheets-Sheet 1 Tlcllo VIII/[111117 zzzzzzzzazzz I 1 INVENTOR flow/4 1: 4. Fpomsaw ATTORNEYS 2 Sheets-Sheet 2 H. A. F ROMSON METHOD OF MAKING TUBING July 27, 1965 Filed July 16, 1959 I 26 v 22' a INVENTOR flan 4P1: ,4. FRO/W80 ATTORNEYS United States Patent Howard A. Frornson, Rogues Ridge Road, Weston, Conn. I

Filed July 16, 1959, Ser. No. 827,628 1 Claim. (Cl. 721 99) This invention relates to the production of thin-walled metal tubes by a combination of extrusion and rolling techniques. More particularly, it relates to a method of producing thin-walled metal tubes having thickened ends suitable for welding or receiving pipe threads.

An object of the invention is the production ofthin walled metal tubes having relatively thick-walled ends.

A further object is the production of thin-walled tubes having relatively thick-walled segments along their length intermediate the ends.

Another object is the production of thin-walled tubes havingrelatively thick-walled segments and having side fins attached to the sides of the thin-walled tubes for bracing and fastening purposes.

Other objects of the invention will be apparent from the following description read in connection with the accompanying drawings, in which FIGS. 1 and 2 are respectively end and side views of a tubular member;

FIG. 3 is a cross-section on plane 3-3 of FIG.

FIG. 4 is a cross-section on plane 4-4 of FIG. 5;

FIG. 5 is a side view of the tubular member shown in FIGS. 1 and 2 after the collapse of a central segment thereof;

FIG. 6 is a cross-section on plane 66 of FIG. 7;

FIG. 7 is a side view of the tubular member shown in FIG. 5 after the collapsed central segment has been rolled to a ribbon-like form;

FIG. 8 is a cross-section on plane 88 of FIG. 9;

FIG. 9 is a side view in partial section of the collapsed tubular member of FIG. 7 after expansion;

FIGS. 10 and '11 are respectively end and side views of the tubular member shown in FIG. 2 collapsed along its full length;

FIG. 12 is a side view of the collapsed tubular member of FIG. 11 after a central segment has been rolled to a ribbonlike form;

FIG. 13 is a cross-section on plane 1313 of FIG. 12; and

FIG. 14 is a side view of the collapsed tubular member shown in FIG. 11 after two segments have been rolled to a ribbonlike form.

The present invention involves the production of a relatively short, thick-walled tube blank 20 by any suitable means. When aluminum tube is desired, such a tube may economically be extruded. The tube blank is coated on its inside surface 21 with a stop-off material to prevent welding together of the opposed inner surfaces during later fabrication steps. Where aluminum is used, lubricating oil may be used. Stop-cit materials suitable for other metals are known to metalworkers; a thin coating of finely divided clay suspended in water will generally suflice.

The prepared tube blank is inserted between the rolls of an ordinary rolling mill and a central segment thereof rolled fiat, without reducing the wall thickness, giving rise to the partially collapsed blank of FIGS. 3, 4 and 5. The collapsed blank is then repeatedly rolled over the segments which it is desired to reduce to a thin-walled tube, leaving the end segment 22, 22 unrolled.

The resulting rolled segment of the blank will be found to have elongated considerably, since very little side spread occurs during rolling. The result is the collapsed 3,195,657 Patented July 27,1965

thin-walled tube of FIG. 7 having open thick-walled end segments 22, 22 at the ends. This collapsed form may be restored to hollow shape by inserting a mandrel in the end segments to open the unbonded central fissure 23 to restore the circular cross-section. The thin-walled segment may beinfiated by applying hydraulic pressure to its interior or by a mandrel.

The final product shown in FIGS. 8 and 9 will be found to have an inside diameter substantially the same as that of the thick-walled tube blank. The outside diameter of the thick-walled end segments will be substantially the same as that of the thick-walled tube blank, while the distance between the outer edges 24, 24 of fins 25, 25 will also approximate the outer diameter of the tube blank. Fins 25, 25 will be found to have a thickness twice the Wall thickness at the thin-walled segments.

The final tube of FIGS. 8 and 9 has several advantages. The thick-walled end segments are well adapted to accept coupling means, such as clamps or threaded couplings, since they may be threaded and will stand compression without collapsing inward. In addition, the metal thickness is desirable for Welding together of successive tube lengths. The thickened ends may also serve as points of support for the tube.

The tube may be rolled and shipped in the collapsed form of FIG. 7 with a great saving of space. Inflation into the form of FIG. 9 may thereafter take place at the location Where the tube is to be used.

The thin-walled intermediate segment obviously allows considerable saving in the cost of metal and in tube Weight. This section will be found more flexible than the thick ends. The thin-walled sections may be supported by brackets which clamp to the side fins thereon.

FIGS. 10 to 13 show a variation in which the full length of the tube blank 20 of FIGS. 1 and 2 is collapsed completely to collapsed blank 20' of FIGS. 10 and 11. Only the central segment of the tube blank is elongated and thinned by further rolling, to produce the collapsed thinwalled tube 20', 22' of FIG. 12 may be opened by prying of FIGS. 12 and 13. The collapsed end segments 22', open the ends of the central fissure 23' and inserting a mandrel therein. A mandrel or hydraulic pressure will serve to open the thin-walled segment. 7

It will be understood that the collapsed tube blank may first be rolled over its entire length to reduce its wall thickness at all points, and then further rolled at inter mediate points to produce a final tube having thin-walled intermediate segments joining thick-walled end segments, the latter having a wall thickness less than that of the original tube blank.

As may be seen from FIGS. 8 and 9 the present method produces a final tube in which the segments of different wall thickness are connected by a smooth fillet. This is desirable as a means of preventing stress concentrations at the junction points.

FIG. 14 shows a further variation of the invention. A thick central segment 26 has been left in the tube intermediate the ends. Such a segment, after opening over a mandrel, may be desirable at intervals. For example, if the tubing is to be laid horizontally and secured to crossties at intervals, the thickened segments may be made to coincide with the position of the cross-ties, where clamps may be expected to compress the tube. As a further example, such an intermediate segment may provide a point at which a long length of tube may be'cut into pieces having thick-Walled ends.

It will be understood that various changes and modifications in the procedure for making thin-walled tubing g; with thickened segments described above may be made by those skilled in the art without departing from the scope of the invention as defined by the following claim.

I claim:

In a method of producing thin-walled metal tubing having integrally connected adjoining segments of different Wall thicknesses, the steps which comprise collapsing a segment of a hollow tubular blank to a flattened striplike form with opposing interior surfaces of said collapsed segment being coated with a weld preventing material, said collapsed segment being integrally connected to an adjoining segment of the blank, and then rolling said collapsed segment of the blank in a lengthwise direction between cylindrical pressure rolls whereby the rolled segment is elongated in length and simultaneously reduced to a constant thickness which is less than twice the wall thickness of the adjoining unrolled segment of the blank, and expanding the formed, collapsed segment of the blank into a hollow tube by separating the opposing interior surfaces thereof.

References Cited by the Examiner UNITED STATES PATENTS 2/20 Frauenheim. 3/34 Chase et al. 7 12/35 Esser 29544 12/35 Wefing 29-544 12/ 43 Harrington 80-62 10/ 44 Orr et al 13 8-47 5/51 Tyson 13847 6/56 Draper et al 29--42l X FOREIGN PATENTS 3/93 Great Britain. 11/96 Great Britain. 12/22 Great Britain.

WHITMORE A. WILTZ, Primary Examiner.

2 LEWIS LENNY, HYLAND BIZOT, Examiners.

ULLLJ'JU uinino 111L111 ULIILJL CERTIFICATE OF CORRECTION Patent No. 3,196,657 July 27, 1965 Howard A. Fromson It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Colump 2, line 39, after "tube 20" insert of FIGS. 12 and 13, The collapsed end segments 22 same column 2, line 40, strike out "of FIGS. 12' and IS. The collapsed end segments 22:,

Signed and sealed this 15th day of February 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

